Semiconductor production equipment or semiconductor conveyance equipment is used under circumstances such as a plasma atmosphere, a chemical atmosphere and an ozone atmosphere, so that a rubber material used in such equipment requires plasma resistance, chemical resistance and ozone resistance, as well as purity that constituent components are not eluted from the material.
To such requirements, a fluororubber molded article is frequently used as the rubber material (for example, see patent document 1 specified below). However, the fluororubber molded article requires the use of a crosslinking agent for securing mechanical strength, so that there is the possibility that an unreacted moiety of the crosslinking agent and crosslinking degradation products are eluted. This raises a problem with regard to purity.
Of the fluororubbers, a tetrafluoroethylene-propylene copolymer is crosslinked by irradiation of ionizing radiation without using the crosslinking agent, thereby also sufficiently securing mechanical strength. Accordingly, there is no problem with regard to purity derived from the crosslinking agent. However, not only the tetrafluoroethylene-propylene copolymer but also a solid rubber generally contains metal elements derived from a polymerization catalyst, an emulsifier and a metal salt used in coagulating a raw latex. Accordingly, when such a rubber material is used as a sealing material, for example, in semiconductor production equipment utilizing plasma gas or ozone gas, there is a fear that the rubber material is decomposed to vaporize, so that the metal elements contained therein emerge in the form of particles to contaminate a semiconductor.
Further, sealing materials are ordinarily used in a state where tensile stress or compression stress is applied. When the sealing material comprising the fluororubber molded article is exposed to the plasma gas or the ozone gas under such stress, it is cracked within a short time to cause a leak.
Patent Document 1: JP 2000-119468 A